Stem structure for electron tubes



INVENTOR. 6to/*don Z/z/O w65 BY a Dec. 20, 1949 yfrs 'A'.HQWES STEMSTRUCTURE FOR ELECTRON TUBES Filed June 2, 1947 .IIA mn..

Patented Dec. 20, 1949 STEM` STRUCTURE FOR ELEGTRGN'TUBES' Gordong T.Howes,y Belmont., Galifa, assigner?v to;` EitelMcCullcugh. Inc.,r San-Bruna Cama., a corporation ofCalfornia Application June 2, 1947, SerialNo. 751,847

1 Claim. l

The invention relates to electron tubes such as vacuum tubes, and moreparticularly to an improved stem structure for such tubes.

The principal object of the invention is to provide a compact stemstructure which affords terminal connectors for an electrode land alsoprolvides an exhaust tubulation for the tube envelope.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, ywill be set forth in the followingdescription of my invention. It is to be understood that I do not limitmyself to this disclosure of species of my invention as I may adoptvariant embodiments thereof within the scope of the claim.

Referring to the drawing the single figure is a vertical sectional viewof an electron tube embodying the improvements.

In terms of broad inclusion, the improved electron tube comprises anenvelope enclosing an electrode, and a tubul-ar metallic stern member onthe envelope, which member is ported into the envelope to provide anexhaust tubulation and projects externally of the envelope to provide aterminal for the electrode, the outer end of the member having its sidewalls compressed together to close the tubulation. In the preferredconstruction a pair of coaxial stem members are provided, the inner ofwhich serves as the exhaust tubulation.

In greater detail, and referring to the drawing, the improved stemstructure is shown in a diode type of electron tube, it being understoodthat the improvements may be incorporated in tubes having moreelectrodes such `as triodes or the like. The tube illustrated is a4diode of small physical size adapted for use in compact spaces such asin a probe, and comprises an elongated evacuated envelope having acylindrical 4wall section 2 of vitreous material such as glass. An anode3 at one end of the envelope is formed by the inner end of a metallicrod 4 such as tungsten sealed to the upper end of the wall section 2.

A cathode is supported by the improved stem structure at the other endof the envelope. This stem structure comprises an outer tubular metallicstern member 1 sealed to the lower end of wall section 2, and an innermetallic stem member 8 coaxial with the outer member. These stem membersprovide terminal connectors for the cathode, and by their coaxialarrangement are adapted for plugging into a socket or the like. Theinner stem member 8 is also tubular and is ported into the envelope toprovide an exhaust tubulation. After evacuation the tubular member 8 ispinched off at tip 8 to compress the side (Cl. Z-27.5)

2 walls of the tubulation together to seal the envelope. To facilitatethis pinching off operation the inner stem member 8 is preferably madeof a relatively soft metal such as copper.

An extension II of thinner wall metal tubing is brazed to member 8 andis aligned with another section of tubing I2. These sections areconnected together and electrically isolated by a sealing ring I3 ofvitreous material such as glass. A metal supporting sleeve I4 is bracedat the upper end to stem section I2 and at the lower end to outer member'I at Ibraze I6. By this arrangement the inner parts of the stemstructure may be assembled as a unit and inserted into the open end ofthe outer stem member 1, the parts being finally secured together by thebraze I6 iat the lower registering edges.

The cathode illustrated is of the indirectly heated type comprising anemitter body I1 heated by a resistance coil I8. Body I1 may be of nickelcoated with suitable oxides for electron emission purposes, inaccordance with the common practice of making cathodes of this kind. Thecathode body I1 is connected to the outer stem member 1 -by supportingwires I9 projecting from tubular piece I2. Heater coil I8 is surroundedby ya heat shield 20 and is connected at the upper end to cathode bodyI1 and at the lower end to a center rod 2I secured to inner stem member8. A ring 22 formed at the lower end of rod 2| facilitates brazing thisrod in position. By these connections it will be seen that the cathodebody is connected to the outer stem member and that the heater isconnected across the inner and outer stem members. It is understood thatthe cathode may be of the filament-ary type such as a thoriated tungsteniil-ament, in which case the filament would be connected across theterminal members in a manner similar to the heater coil I8.

In order to shield the envelope and other parts of the tube frommaterial sputtered from the cathode a tubular metal shield 23 ispreferably mounted on sleeve I 4 to project upwardly inito the regionssurrounding the cathode. For similar reasons a transverse shielding disk24 is preferably provided below the cathode body, held in shield 23 by aretaining ring 26. It is understood that the entire cathode structure ismounted on the inner stem assembly prior to inserting sleeve III intothe outer stem member 1. After inserting the inner stem assembly theiinal braze I6 is made to complete the envelope. At this stage thetubulation member 8 is, of course, open ended for purposes of exhaustingthe envelope. Following evacuation the exhaust tubulation is pinched offat tip 9 to seal the envelope and leave the tubulation in condition tofunction as a terminal member.

The improved stem structure above described, incorporating the exhausttu-bulation as a terminal connection for the cathode, has specialadvantages in tubes of small 'physical size where space is at a premium.

I claim:

An electron tube comprising electrodes and an 10 of the envelope toprovide an exhaust tubulation 1 and rprojecting externally of theenvelope. the

outer end of said member having its side walls compressed together toclose the tubulation, said outer projecting end being exposed externallyof the envelope to provide a rigid terminal prong.

GORDON T. HOWES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,431,337 Litton Nov. 25, 19472,455,957 Spencer Dec. 14, 1948

